Radiused backs and strength

berberiv

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Hi, all,
I don't believe I've posted before. My name is Viktor, I've built several guitars and basses and am working on my third concert ukulele.
Just curious about this:
I like the look of a slightly radiused back, but I'm skeptical of the notion that the arch makes the back stronger. (I've heard this a number of times.) An arch may resist downward force, but not lateral force (from the side). Downward force is an issue on archtop guitar tops (or violins, etc.), but there seems to be no downward force on the back any of these instruments, including ukuleles.
I believe that arching the back introduces tension (this is an important element in violin construction, for example)--but I really don't see how it would make the back stronger? Do you believe it makes the back more rigid (and reflect better)?
 
I think most people introduce an arch not simply for strength, but to resist changes in humidity and therefore a protection against the wood drying out, shrinking and cracking. And the (in my view) misguided belief it somehow reflects sound better.
 
Question for Alaine: Why would you want the backs responsive. The early elite instruments of a well known ukulele brand ran into trouble because of this very thing - the back 'stealing' energy from the front. You want all the power and energy in the front hence laminated sides which kill vibration transfer to the back. The back needs to be stiff and profoundly radiused. If you want to learn more about design I am running a zoom event next Saturday on Facebook. This is not SSP since you will have to hunt around to find the details.
 
A responsive (or live) back is a good thing on guitar, So my thinking was that it should be good also for Ukulele! But I have been wrong before!
I said it seems to be less responsive because when tapping and recording the frequencies it was very difficult to see a difference between the top and back curves. Tapping the top or tapping the back gave almost the same peaks, which was not the case with my previous flatter backs.
So may be the reason is that these backs are more reflecting than responsive which, like you say, might be a good thing. I am still learning!
What does SSP stand for ? This event will be on your Facebook group?

Alain (without e) :eek:
 
I have a much better sense of what constitutes good tone in an archtop guitar than I do in a ukulele. Like Alain, my sense is that responsiveness is good in a guitar (for tone, and perhaps complexity of tone), but that it has to be balanced with stiffness/reflection for volume. Is volume the more important concern in a ukulele?
Red Cliff's response about resisting cracking makes perfect sense to me. Thanks!
 
Maybe the sting instruments that are not held against body while being played are best for back response eg: the violin family Cello Double base etc..that is why they have a sound post under the bridge to transfer the vibes to the back of the instrument thus increasing the volume...maybe a double back and sound post would also work on a uke.
 
There are two schools of thought, the traditional (i.e. live back) and the more modern non-live back i.e. Smallman. I guess there are degrees between the two extremes. You can be sure that there's no wrong or right, it all depends on what you consider to be 'the best'. We tend to have different ideas on that.
As for flat and arched backs. I've made many of both. I can't say that I've come to any firm conclusion of one being better than the other. Nor have I had a flat back crack. However flat backs (over time) do tend to sink and show a bit of concavity after being subject to the inevitable fluctuations in humidity. They don't tend to recover when brought back to higher humidity either. Not sure that the slight concavity is much of a problem though.
 
Did you read my response? This is not theory it is practical. The company concerned had to sell at cost a whole huge batch of instruments and go back to the drawing board. I value the real thing over theoretical considerations. And yes, if I was building a flamenco guitar I'd want the whole thing to be shuddering as a played it! I haven't said this for a long timer - ukulele are not guitars.... The soundpost only works because by it, the plates are coupled and the whole instrument resonates. It's why you have to have a different 'carve' for the front and back - if they were the same you'd get 'wolf' notes.
 
Sorry Pete, but I have to disagree. Live backs can clearly cause issues with resonances and wolf notes if not careful. Solid sides and stiff back can mitigate some of that. But it is possible to have a live back, thin sides and still have a great instrument without wolf notes. In fact the classical guitars through history (e.g. hauser etc) that people tend to associate with the best sound (to their ears) tend to be traditionally braced with live backs and thin sides. The more modern approaches ( reinforced sides, double tops, laminated stiff backs etc) have increased volume, but haven't on the whole produced better sounding instruments, at least not to my ears. And that isn't theory, but is practical. I think taking one example where it hasn't worked and ignoring the thousands where it has is being very selective of the evidence. If it works for you then great, but there is more than one way to skin a cat.
 
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Warnign:

I am expressing 'my views' not 'the view'. I've done this before and upset people who post here. I am not saying you are wrong, though I strongly challenge your views. This is called 'debate' and at the end of it we should still remain friends. If you don't like your views being challenged then don't read this response to what I think are great ideas; not just the ones I hold.

Guitars again.... show me a uke which is damped that has a live back and sides that is 'better' than one that is not. I just don't hold with the argument - it's not compelling enough and there is not enough empirical evidence for UKULELE to prove it. Citing the extensive research and contradictory evience in the classical guitar world (note, none in the steel string) and the woeful lack of consistent scientific and controlled experiment papers on it, this debate becomes a 'he said/she said' argument of no merit.

I began my building career in academia an have done some research - my dissertation was on the history of the classical guitar. I interviewed makers who built differently and drew my own conclusions. When I began my full time career as a ukulele maker I followed tradition. Today I have thrown all fo that away to experiment and test tropes - which is what these arguments are. If you are going to make a statement about something then, in my view, it is only real if you have evidence to back it up. I gave the evidence... where is yours?

In this world of making where opinion is misrepresented as fact it is easy, without any qualifying experience to state that x is better than y when you haven't defined what 'better' is. "Better' in this context would more accurately be defied as "The sound I like." For the record, I have no documented papers on the subject. I make my living from doing not thinking about doing. So here is my 'evidence' of a recent , non regulated or documented experiment:

I have just altered the bracing on my concert design and hope that the second instrument I have built with this bracing (the first was an assisted student build made in tandem with her but not yet finished) will be as 'good' as the first. I'll know and report in follow up here, later in the week. What I do know is:
!: My 'new' bracing is only new to me - I know others have done it. I research and try other's ideas out that make sense to me and have rarely been wrong in my considerations when facd with the resulting piece built.
2: I am 'tying' my front braces into the lower block and top front bar - something your 'are not supposed to do' according to those who have views on the subject. This little nugget I gleaned from a flamenco guitar maker....
3: I've increased from former designs the thickness of the backs including the braces that hold the 12' radius - something I have not yet changed but may do in the future if I ever build another concert.
4: I've 'floated' the front rather than 'stressed' it onto the rims - again from my flamenco guitar maker friend. New departure for m.
5: I don't know if thsee two instruments sound 'better' than the 971 I have previously built, What I do know is I have never hear a louder concert from my bench that has retained it's sweetness like this one that my student and I finished an set up yesterday:. This is my 'evidence' for what it is worth.



Final plea. Could those who build provide sound samples please. Build documentation is great but rarely do we get a demo....
 
Hi Pete. I'm always interested to hear what others are trying when it comes to bracing. However, I don't understand what you mean by 'floated' as oppose to 'stressed' when talking about the top in point 4. Please could you explain what you mean.
 
Warnign:

2: I am 'tying' my front braces into the lower block and top front bar - something your 'are not supposed to do' according to those who have views on the subject. This little nugget I gleaned from a flamenco guitar maker....

4: I've 'floated' the front rather than 'stressed' it onto the rims - again from my flamenco guitar maker friend. New departure for m.

Same thing here, I cannot visualize these 2 points as they seems to go in opposite directions. Can you elaborate please.
 
Warnign:

I am expressing 'my views' not 'the view'. I've done this before and upset people who post here. I am not saying you are wrong, though I strongly challenge your views. This is called 'debate' and at the end of it we should still remain friends. If you don't like your views being challenged then don't read this response to what I think are great ideas; not just the ones I hold.

Guitars again.... show me a uke which is damped that has a live back and sides that is 'better' than one that is not. I just don't hold with the argument - it's not compelling enough and there is not enough empirical evidence for UKULELE to prove it. Citing the extensive research and contradictory evience in the classical guitar world (note, none in the steel string) and the woeful lack of consistent scientific and controlled experiment papers on it, this debate becomes a 'he said/she said' argument of no merit.

I began my building career in academia an have done some research - my dissertation was on the history of the classical guitar. I interviewed makers who built differently and drew my own conclusions. When I began my full time career as a ukulele maker I followed tradition. Today I have thrown all fo that away to experiment and test tropes - which is what these arguments are. If you are going to make a statement about something then, in my view, it is only real if you have evidence to back it up. I gave the evidence... where is yours?

In this world of making where opinion is misrepresented as fact it is easy, without any qualifying experience to state that x is better than y when you haven't defined what 'better' is. "Better' in this context would more accurately be defied as "The sound I like." For the record, I have no documented papers on the subject. I make my living from doing not thinking about doing. So here is my 'evidence' of a recent , non regulated or documented experiment:

I have just altered the bracing on my concert design and hope that the second instrument I have built with this bracing (the first was an assisted student build made in tandem with her but not yet finished) will be as 'good' as the first. I'll know and report in follow up here, later in the week. What I do know is:
!: My 'new' bracing is only new to me - I know others have done it. I research and try other's ideas out that make sense to me and have rarely been wrong in my considerations when facd with the resulting piece built.
2: I am 'tying' my front braces into the lower block and top front bar - something your 'are not supposed to do' according to those who have views on the subject. This little nugget I gleaned from a flamenco guitar maker....
3: I've increased from former designs the thickness of the backs including the braces that hold the 12' radius - something I have not yet changed but may do in the future if I ever build another concert.
4: I've 'floated' the front rather than 'stressed' it onto the rims - again from my flamenco guitar maker friend. New departure for m.
5: I don't know if thsee two instruments sound 'better' than the 971 I have previously built, What I do know is I have never hear a louder concert from my bench that has retained it's sweetness like this one that my student and I finished an set up yesterday:. This is my 'evidence' for what it is worth.



Final plea. Could those who build provide sound samples please. Build documentation is great but rarely do we get a demo....


Pete, I don't need any evidence, it's a discussion forum. But if we are going there, you haven't given any evidence, you have given your opinion. That may well be an opinion based on a lot of experience, but it is still just an opinion, not a fact.

You can't complain people haven't supplied empirical evidence when you haven't either. Finding a single event (one company) that agrees with your hypothesis is not evidence, it is selection bias. Telling us what you do or have done and that it works is not evidence - I could just as well do the same.

I thought the idea of a discussion forum is to have a discussion. You have a view, I have a different one, and that is fine. If it works for you then great. But there are other ways.
 
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